1. Field of the Invention
Embodiments of the present invention generally relate to testing of partially or fully completed semiconductor devices, and more particularly, to resilient contact elements for use in a probe card assembly for testing such devices.
2. Description of the Related Art
When testing partially or fully completed semiconductor devices formed on a semiconductor substrate, such as integrated circuits and the like, a contact element is typically brought into contact with the device to be tested—also referred to as a device under test (or DUT). The contact element is typically part of a probe card assembly or other similar device coupled to a test mechanism that provides electrical signals to terminals on the DUT in accordance with a predetermined testing protocol. This testing is typically done in a controlled environment (e.g., a clean room) to minimize the size and number of particles in the testing environment. However, even when testing in a controlled environment, and more particularly in situations where testing is not performed in a controlled environment, particles may become disposed on the surface of the DUT may interfere with the testing. Moreover, such particles may further deform or break the contact elements disposed in the probe card assembly when a particle strike occurs.
For example, FIG. 1 depicts a conventional contact element 100 including a beam 104 and a tip post 106 having a tip 108 formed or disposed at a distal end of the tip post 106 and configured for contacting the DUT during testing. The beam 104 is coupled to a post 102 at an end opposite the tip 108. The post 102 is utilized to couple the contact element 100 to a probe card assembly. A particle 112 may be disposed on a surface of a substrate or DUT (illustratively depicted in FIG. 1 as reference plane 110) and thereby interfere with testing the DUT. If the tip 108 and/or tip post 106 comes into contact with the particle 112, a misprobe may occur and the contact element 100 may be further be deformed or deflected to a position such that the contact element 100 becomes permanently deformed (i.e., the contact element undergoes plastic deformation). Such plastic deformation may occur even where the particle 112 contacts the beam 104 at any other point along its length including beneath the post 102. Moreover, depending upon the particle size and the quantity of deflection of the contact element 100, the post 102, beam 104, or tip post 106 may break and become detached from the probe card assembly, particularly in instances where the particle contacts the contact element 100 near or beneath the post 102.
One method to try to decrease the probability of a particle strike is to increase the length of the tip post 106, thereby raising the height of the beam 104 with respect to the reference plane 110. However, such a design undesirably increases the scrub of the contact element (the forward distance that the tip moves after contacting the surface of the DUT, sometimes referred to as the scrub ratio when dividing the forward distance moved by the tip by the downward distance moved by the contact element after initial contact with the DUT).
Therefore, there is a need in the art for an improved contact element.